CHICAGO — Patrick Fitzgerald, one of the most feared U.S. attorneys in the nation and the architect of convictions against two Illinois governors and a former vice presidential aide, announced Wednesday that he is stepping down from the post he has held for more than a decade in Chicago.

Fitzgerald has overseen thousands of criminal prosecutions and high-profile cases, including against Illinois governors Rod Blagojevich and George Ryan, former Vice President Dick Cheney's top aide I. Lewis "Scooter" Libby and media mogul Conrad Black. He took on public corruption, international terrorism, corporate fraud and organized crime.

His office announced Wednesday that he's stepping down effective June 30.

A statement from his office gave no reason for his decision to leave the presidentially appointed post he has held for Northern District of Illinois since Sept. 1, 2001. It said he did not immediately have any future employment plans and would take the summer off before considering other job possibilities. He was scheduled to address a press conference on Thursday morning in Chicago.

In the announcement, Fitzgerald recalled how upon his appointment to the post he considered it "one of the greatest opportunities that one could ever hope for."

"I believe that even more now after having the privilege of working alongside hundreds of dedicated prosecutors and agents," he said in the statement.

Fitzgerald is leaving the Justice Department after nearly 24 years, including his time as an assistant U.S. Attorney in New York.

As the top federal law enforcement official in northern Illinois, Fitzgerald was at the center of some of the biggest legal stories in Illinois history, including corruption convictions against Ryan and Blagojevich — the latter of which was tried for a second time after jurors deadlocked on all but one charge in his first trial.

Nationally, Fitzgerald was tapped to be the special prosecutor in Washington's CIA leak case, eventually convicting Libby for perjury and other offenses.

Fitzgerald became one the most feared U.S. attorneys in the nation since he took over in 2001, winning convictions for several city workers and trucking executives, as well as some of top figures in the administration of former Chicago Mayor Richard Daley.

It was his reputation as a hard-charging prosecutor that got him the job in the first place. As an assistant U.S. attorney in New York he successfully prosecuted major terrorism cases including against those responsible for the 1998 bombing of two U.S. embassies in East Africa and Omar Abdel-Rahman, the so-called "blind sheik," convicted in 1995 of plotting to bomb the Holland Tunnel and other key sites around New York city.

The statement from his office said Fitzgerald has notified the White House, Attorney General Eric Holder and Illinois' two U.S. senators of his decision.